This research seeks to gain understanding of the interactions between genetic and nutritional factors in the development of mammals, and of the influence of nutritional factors on the teratogenicity of drugs. Specific aims include a) further characterization of the interaction between the mutant pallid and manganese metabolism, b) establishment of other interactions of mutant genes or inbred strains with trace elements, and c) determination of the influence of nutritional factors on drug effects during prenatal development.